honestly, i like dmc4 a lot, way ahead of a lot of similar games, and not that much less than 3, and to the extent i tend to downplay that like, it's because i do ultimately get why people feel negatively and would hate to overpromise on the game, haha. but i'd consider it my second favorite in the series and probably the genre as a whole, so it really made me happy to see you "get it" too, especially as someone who i assume is not going to go and play the game for another 40 hours. (really, i specifically held off saying so because i didn't want to do so only for it to fall flat by the ending...) i really do think a lot of it has aged relatively well, and as you've mentioned, i think a lot of it comes from the ways that it didn't align with a lot of the accepted design of the time and kind of "settled" for being an (even more combat-focused) sequel to 3
nero's mechanics are funny to me, i think it's clear they wanted him to feel more straightforward but as a result they made the entry to his best stuff feel very steep, which i think a lot of people find off-putting. i think he feels fine at a basic level and really satisfying to feel the best parts come together if you stick with it, but i recognize the disappointment of being stuck halfway. dante in this game is an incredible kind of nonsense and i think if anything they toned down a the individual styles to make up for having everything all the time, which on balance feels like a buff for the usefulness of royal guard and gunslinger even if the former's outrageous damage in 3 has been toned down in return. there's a lot of cool videos out there.
SE vergil is pretty similar to his version in 3, though he similarly feels a bit less overpowering to everything, and i think lady and trish's game is the coolest addition to the rerelease. lady is a bit like nero, and plays on his stages, with a lot of power and a couple of unique tools covering a relative lack of overall options. and trish's game gets a little rude in spots since her damage is really low and she's more designed around control that doesn't work well on a couple of especially annoying enemies and bosses. but i definitely think you might have a good time with that.
honestly, i've played both games to the point that the difference between 3's "remixed" areas and 4's obvious retreading stopped being something i cared about, but the parts where i really, really think 3 wins out are the story (and its corresponding late 90s/early 2000s action movie vibes compared to 4 being more of...a jrpg) and music. and even then they came up with one really good dmc song for the credits. hahahahahahahaha